1. Field of the Invention
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire suitable for a high performance vehicle, in which wet condition drainage ability, controlling stability and tire wear resistance can be altogether improved without detracting from other tire properties.
2. Description of the Related Art
Conventionally, in order to suppress the occurrence of hydroplaning during high speed running, a plurality of straight line grooves extending along a direction of travel, i.e. along a circumferential direction of a tire, are disposed at a vicinity of a tire center line.
However, when a relatively large number of straight line grooves, are formed so as to suppress the occurrence of hydroplaning, ground contact area is reduced and impairment of dry condition properties becomes a problem.
Recently, moreover, as vehicle performance has risen, there has been demand in the market for further improvements in wet condition running properties.
The present invention is provided to solve the above-described problems and an object of the present invention is to provide a pneumatic tire suitable for a high performance vehicle, in which wet condition drainage ability, controlling stability and tire wear resistance can be altogether improved without detracting from other tire properties.
In a first aspect of the present invention, a pneumatic tire for mounting to a wheel and supporting a vehicle above a surface, the tire comprises a tread having opposite edges and a surface contact portion when the tire is supporting a vehicle.
The tread includes: (a) a central circumferential main groove extending circumferentially around the tire and dividing the surface contact portion substantially into two equal halves; (b) an inboard side area extending from the central circumferential main groove towards the inboard side tread edge when the tire is supporting a vehicle, the tread having a negative ratio from 34% to 39% in the inboard side area; and (c) an outboard side area extending from the central circumferential main groove towards the outboard side tread edge when the tire is supporting a vehicle.
The tread has in the outboard side area: (i) a negative ratio from 35% to 37%; (ii) a plurality of lateral main grooves, each lateral main groove having a beginning end opening into the central circumferential main groove and slanting away from the central circumferential main groove at a first angle relative to the tire circumferential direction, to an opposite end opening at the outboard side area tread edge, the first angle being in a range of 55xc2x0 to 90xc2x0 and increasing in a direction along each lateral main groove towards the outboard side area tread edge, adjacent lateral main grooves being spaced from 45 mm to 50 mm from one another along the tire circumferential direction, and each lateral main groove having a width from 6 mm to 10 mm, with its beginning end located further toward a direction of rotation of the tire relative to the opposite end when the tire is rolling forwardly as used on a vehicle; (iii) a plurality of slanted longitudinal main grooves, each slanted longitudinal groove having a beginning end opening into a lateral main groove and extending at a second angle relative to the tire circumferential direction, at least to a terminating end in a vicinity of the outboard tread edge, the beginning end being located further toward the direction of rotation of the tire relative to the terminating end of the slanted longitudinal groove when the tire is rolling forwardly as used on a vehicle, the second angle being in the range of 5xc2x0 to 50xc2x0 and increasing in a direction along each slanted longitudinal groove towards the outboard area tread edge, each slanted longitudinal groove intersecting a plurality of lateral main grooves, with at least three intersections, the at least three intersections nearest or at the beginning end of the slanted longitudinal groove being located 9% to 35% of a width of the surface contact portion from the central circumferential main groove, in the outboard direction, each slanted longitudinal main groove having at each of the at least three intersections a width of 50% to 120% of the width of the beginning end of the lateral main groove which opens into the central circumferential main groove; and (iv) a plurality of land portions each separated from one another by the slanted longitudinal and lateral main grooves.
The present aspect provides the following excellent effects:
a) During high speed running along a wet road surface, water at the ground contact center line is drained in a tire forward direction. Because the central circumferential main groove is disposed at the ground contact center line so as to extend along the tire circumference direction (practically the same direction as the tire forward direction), the water at the ground (surface) contact center line can be efficiently drained from inside the ground contact area with little drag from water.
b) Water in the vicinity of the ground contact center is drained substantially in the tire forward direction or at a slight angle (5xc2x0 to 30xc2x0) to the tire forward direction. In the present aspect, the outboard side slanted longitudinal main grooves are provided in the tread such that a ground contact center line end thereof opens into one of the outboard side lateral main grooves, another end of the outboard side slanted longitudinal main groove extends to an outboard side tread edge vicinity, and the angle of the outboard side slanted longitudinal main groove with respect to the tire circumferential direction gradually increases in a range 5xc2x0 to 50xc2x0 from the ground contact center line to the outboard side tread edge. Moreover, at least the first three intakes of the outboard side slanted longitudinal main groove, as counted from the ground contact center line end, open into corresponding outboard side lateral main grooves within an area of 9-35% of the ground contact width in the outboard side area. Each outboard side lateral main groove and each outboard side slanted longitudinal main groove is slanted such that the ground contact center line side thereof is disposed further toward a tire rotation direction than the tread edge side thereof. Consequently, water in the vicinity of the ground contact center can be drained very effectively.
c) At the opening portions of the outboard side slanted longitudinal main grooves into the outboard side lateral main grooves, the groove width, at least of the opening portions through to the third intake counting from the ground contact center line toward the ground contact edge, is 50% to 120% of the groove width of the inboard lateral main groove openings into the central main groove. Therefore, water can be drained from the central circumferential main groove to the tire axial direction outer side very effectively.
d) The negative ratio in the inside area of the tread is in the range 34% to 39%, and the negative ratio in the outside area of the tread is in the range 35% to 37%. Accordingly, wear resistance and controlling stability are assured.
e) Because one end of each outboard side lateral main groove opens into the central circumferential main groove, another end of each outboard side slanted lateral main groove opens at an outboard side tread edge, and the angle of each outboard side lateral main groove with respect to the tire circumferential direction increases, within a range 55xc2x0 to 90xc2x0, from the ground contact center line side to the outboard side tread edge side, water in the vicinity of the ground contact center can be drained very effectively.
Because of the above-described effects, wet condition drainage ability, controlling stability and tire wear resistance can be altogether improved in a pneumatic tire based on the present aspect.
In a second aspect of the present invention, a pneumatic tire for mounting to a wheel and supporting a vehicle above a surface, the tire comprising a tread having opposite edges and a surface contact portion when the tire is supporting a vehicle.
The tread includes: (a) a central circumferential main groove extending circumferentially around the tire and dividing the surface contact portion substantially into two equal halves; (b) an outboard side area extending from the central circumferential main groove towards the outboard side tread edge when the tire is supporting a vehicle, the tread having in the outboard side area a negative ratio from 35% to 37%; and (c) an inboard side area extending from the central circumferential main groove towards the inboard side tread edge when the tire is supporting a vehicle.
The tread has in the inboard side area: (i) a negative ratio from 34% to 39%; (ii) at least one inboard side circumferential main groove extending circumferentially around the tire between the central circumferential main groove and the inboard side area tread edge; (iii) a plurality of lateral main grooves, each lateral main groove having a beginning end opening into the central circumferential main groove and slanting away from the central circumferential main groove at a first angle relative to the tire circumferential direction, to an opposite end opening at the inboard side area tread edge, the first angle increasing in a range from 55xc2x0 to 90xc2x0 in a direction along each lateral main groove towards the inboard side area tread edge, adjacent lateral main grooves being spaced from 45 mm to 50 mm from one another along a direction of the tire circumferential direction, and each lateral main groove having a width from 6 mm to 10 mm, with its beginning end located further toward a direction of rotation of the tire relative to the opposite end when the tire is rolling forwardly as used on a vehicle; and (iv) a plurality of land portions each separated from one another by the lateral main grooves and the circumferential main grooves, each land portion having a plurality of vertices, with one vertex positioned further toward the tire direction rotation when the tire is rolling forwardly as used on a vehicle, relative to the other vertices of the land portion, with each land portion adjacent to the central circumferential main groove, having a width measured along a transverse direction of the tire, of 20% to 30% of a width of the half of the surface contact portion in the inboard side area, and having the one vertex having an acute angle from 55xc2x0 to 70xc2x0.
In addition to the effects a) through d) described above, the present aspect provides the following excellent effect:
f) One end of each inboard side lateral main groove opens into the central circumferential main groove, another end of each inboard side lateral main groove opens at an inboard side tread edge (vicinity), and the angle of each inboard side lateral main groove with respect to the tire circumferential direction increases, within a range 55xc2x0 to 90xc2x0, from the ground contact center line side to the inboard side tread edge side. Consequently, water in the vicinity of the ground contact center can be drained very effectively by the inboard side lateral main grooves toward the inboard side tread edge (as in item e) above).
Because of the above-described effects, wet condition drainage ability, controlling stability and tire wear resistance can be altogether improved in a pneumatic tire based on the present aspect.
In a third aspect of the present invention, a pneumatic tire of the present invention is used on a front wheel of a vehicle. That is, the characteristics of the present invention can be most remarkably achieved by using pneumatic tires based on the present invention on the front wheels of vehicles.
In a fourth aspect of the present invention, a pneumatic tire based on one of the above aspects is mounted for use on a vehicle with wheel alignment settings such that a toe angle is in a toe-in range 0xc2x0 to 0.7xc2x0 and a camber angle is in a negative camber range 0xc2x0 to 5xc2x0.
That is, the characteristics of the present invention can be most remarkably achieved by using a pneumatic tire based on the present invention mounted on a vehicle with wheel alignment settings such that the toe angle is in the toe-in range 0xc2x0 to 0.70 and the camber angle is in the negative camber range 0xc2x0 to 5xc2x0.